A simple piezometer probe for the routine measurement of pore pressure in triaxial tests on saturated soils

Abstract

A technique has been evolved for installing a piezometer probe on samples down to a diameter of 38 mm. The probe is based on a miniature silicon diaphragm pressure transducer mounted at mid-height to cause minimum interference between the sample and probe and to provide a rapid response for the piezometer-soil system. Considerable savings can be made in testing times by using the probe at mid-height and by using effective lubricated end platens. Measurements can also be made in cyclic loading tests on clays and are viable in quick undrained tests even at shearing rates used in commercial laboratories. Examples are given of measurements made in undrained compression-extension triaxial tests in cromer fill and medium-dense ham river sand. The probe provides a more accurate method of measuring pore pressures in unconsolidated undrained triaxial tests and can be effectively used to maintain an acceptably low gradient of pore pressure in the sample when following a drained stress path. (TRRL)